Engines may use a turbocharger to improve engine torque/power output density. In one example, a turbocharger may include a compressor and a turbine connected by a drive shaft, where the turbine is coupled to an exhaust manifold side and the compressor is coupled to an intake manifold side. In this way, the exhaust-driven turbine supplies energy to the compressor to increase the pressure in the intake manifold (e.g. boost, or boost pressure) and to increase the flow of air into the engine. The boost may be controlled by adjusting the amount of gas reaching the turbine, for example with a wastegate. The wastegate may include a wastegate valve which may be opened to divert gas away from the turbine based on operating conditions to achieve the desired boost. In one example, the wastegate may be electrically actuated by an associated electric actuator. The electric actuator is coupled to the wastegate valve via a mechanical linkage and driven via commanded actuator positions to control the wastegate valve position, thereby controlling the amount of gas reaching the turbine and achieving the desired boost.
U.S. Pat. No. 8,347,625 describes an electronic wastegate arrangement in which an electric actuator such as a rotary motor is coupled via a rod-like mechanical linkage to a wastegate valve. The electric actuator is positioned a distance away from the wastegate valve, opposite a side of the valve whereat diverted gas flows as the valve is opened.
The inventors herein have recognized several issues with such an approach. As temperatures proximate the wastegate valve are high, the electric actuator is positioned far enough away from the valve operate normally. Accordingly, a sensor indicating a position of the electric actuator is positioned proximate the actuator and away from the wastegate valve. Thus, the actual position (e.g., lift from a valve seat) of the wastegate valve cannot be determined. Material deformation in the linkage coupling the actuator to the wastegate valve due to high temperatures further complicates control of the valve, as a commanded actuator position will result in an inaccurate valve position, in turn causing an inaccurate level of boost to be supplied to an engine.
Systems and methods for determining the lift of a wastegate valve are provided. For example, a method comprises determining a relation between an actuator position and a lift of a wastegate valve at engine start-up in a temperature range. The relation may be modified based on a difference between a desired boost level and an actual boost level.
In this way, the lift of a wastegate valve may be determined such that commanded actuator positions result in the supply of a desired boost level even as material deformation (e.g., elongation) in the valve and mechanical linkage coupling the valve to the actuator occurs in the presence of high temperatures. Thus, the technical result is achieved by these actions.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.